Rationale for sunscreen development.

The risks associated with cumulative or overexposure to ultraviolet (UV) radiation are now well identified. They involve both UVB (290-320 nm) and UVA (320-400 nm) components. UVB radiation is still considered to be the major factor responsible for most harmful effects of solar exposure. But the detrimental role of UVA has been increasingly documented. As a result, the development of a new generation of sunscreens that provide effective protection throughout the whole UV radiation spectrum has become a prime concern and a major issue. These full-spectrum protections must be carefully designed by selecting UV filters with highly reliable stability to ensure optimal safety and efficiency during the entire period of sun exposure. For this purpose, extensive research on the photochemical behavior of various classes of UV filters has been carried out. This has led to the discovery of safe systems that prevent sun-induced degradation of potent UVA filters and to the development of new UVA filters with a high photostability.